The primary job of automobile transmissions is to provide a wide range of output speed for a vehicle while allowing the engine to operate within a narrow range of speeds. The earliest automobiles offered only manual transmissions, but as cars grew larger engineers began searching for a way to allows cars to automatically shift from one gear to another.
Modern electronically controlled transmissions use electric solenoids to control the hydraulic circuits that actuate the clutches and bands. A control unit controls the shift points of the gears based on inputs from various other sensors on the engine and transmission. The control unit detects such parameters as throttle position, vehicle speed, engine speed, engine load, stop light switch position, etc., to control exact shift points, as well as how soft or firm the shift should be.
Current engine/transmission combinations use either a single control unit to control the function of both the engine and transmission or separate controllers for each. These control units are custom designed for each engine and transmission design. Until recently this has not been a problem, since engines and transmissions are usually specifically designed to be used together. However, as automobile production has begun to shift to developing nations, there has been a trend to combine engines and transmissions designed by different manufacturers, particularly for sale in the domestic markets of these developing nations.
The main competitive advantage of these developing countries is lower manufacturing costs, as opposed to technical innovation. Therefore, there is a tendency to use off the shelf designs rather than develop new ones. One consequence of this off the shelf production approach is the mixing and matching of engines and transmissions that were designed by different automotive firms. This raises the problem of properly controlling and coordinating their operation, because the control units are custom designed for specific models and combinations of engines and transmissions. In some cases, the separate controllers on the engine and transmission may have trouble communicating with each other. For example, a transmission control unit may have sensor inputs that differ from the engine's output. In other cases, a transmission that is normally controlled by a single controller in the engine is paired with an engine that does not provide such control. This lack of coordination impairs smooth gear shifting in the transmission.
Therefore, it would be desirable to have a universal transmission control unit that is generic across transmission brands and models and can be custom programmed to accommodate any combination of engine and transmission.